In cities around the world, there has been a growing interest in replacing aging timber electric utility distribution poles and light poles with steel poles. Using galvanized steel utility poles is regarded as having several significant environmental benefits over timber including lower levels of greenhouse gas and aerosol emissions associated with global climate change; a lower burden on critical energy resources; reduced impacts on the habitats of many threatened and endangered species; and reduced impacts associated with hazardous emissions and wastes.
Steel utility poles are also regarded as having a number of other clear advantages over competing materials, for example, treated wood and concrete, including: ease of installation, fabrication with uniform dimensions, reliability, durability, impervious to insects and rot, free of toxic chemical treatments or hazardous waste concerns, completely recyclable, and a lower life cycle cost. It is estimated that there are approximately 185 million utility poles in North America alone and an estimated 2.5 million timber poles are replaced each year.
Unfortunately, planted utility poles of metal commonly experience groundline damage and loss of groundline strength as a result of contact with soils, moisture and oxygen. The walls of these hollow or at least partially hollow poles are typically thin and even if galvanized, the severity of the environmental conditions ultimately determines the lifespan of steel structures. Table 1 below shows atmospheric corrosivity categories and approximate life cycles to first maintenance (in years) for galvanized planted streetlight poles according to Australian Standards. The groundline zone of the pole also coincides with the highest bending moment of the structure and consequently the highest areas of stress. Any significant loss in strength capacity can result in the failure of the structure.
TABLE 1System Designation HDG500 Life to First Maintenance to A52312Atmospheric corrosivity categoryE-IE-MVeryVeryFABCDHighHighInlandVery lowLowMediumHighIndustrialMarineTropicalLFM25+25+25+10-25NR5-1025+
Current methods for addressing groundline damage to planted utility poles include welding, bolting or strapping the pole to increase strength in the region of the groundline.
An aim of the present invention was to overcome substantially, or at least provide a useful alternative to, the above-mentioned problems associated with the prior art.
The preceding discussion of the background art is intended to facilitate an understanding of the present invention only. It should be appreciated that the discussion is not an acknowledgement or admission that any of the material referred to was part of the common general knowledge as at the priority date of the application.